PS3 Syscall questions regarding PSL1GHT

[Bep0iaa1]

I recently worked on a project that makes disc backups bootable from the XMB as NPDRM.
Since I'm not very knowledgeable in this scene, I only had two concepts that came to mind:

1. To write an executable that first remaps the game's backup folder with a syscall to /app_home and then launches it. It turned out that it refused to boot into the game unless it was mounted at /dev_bdvd.
   
2. To resign the EBOOT and change the SFO.

I chose the first option since the second one could be problematic. For one, you don't know the game's original code, like if it is hardcoded to read from /dev_bdvd and so on. I created a PoC based on the first idea, which runs perfectly fine (though, of course, slower than a usual NPDRM game, but that doesn't matter for now).
However, since I wrote it with the official SDK, I thought it would be problematic to release the source code, so I decided to port it to PSL1GHT. And here comes the issue. In the original SDK, I use <sys/syscall.h> as well as syscall8 (inspired by Aldo's webMAN), and everything worked fine and smooth, with no complaints. While porting to PSL1GHT, I decided to use ppu-lv2.h, which includes the syscalls. As always, something didn't work as planned, so I added msg to read the (p1) return value from the syscall (which was -1 or 0xFFFFFFFF, btw).

Currently, I'm kind of clueless about how to approach this issue, so I thought I could find some help in this forum. I thought I had found a topic related to calling syscalls, but I can't find it.

If necessary, I can upload the current PSL1GHT port to GitHub for further assistance.